An OLED is an Organic Light Emitting Diodes Display possessing properties of self-illumination, high brightness, wide view angle, high contrast, flexibility and low power consumption, etc., and accordingly has been received more attentions. As being the display of next generation, it has been gradually replaced traditional liquid crystal displays and widely applied in cellular phone screens, computer displays, full color TV, etc. OLED display technology is different from the traditional liquid crystal display technology and the back light is not required. It utilizes an ultra thin organic material coating layer and a glass substrate, and theses organic material will illuminate when the current is conducted.
Please refer to FIG. 1, which is a sectional diagram of an OLED backplate structure according to prior art, comprising a substrate 100, a TFT layer 700 positioned on the substrate 100, a first isolation layer 710 positioned on the TFT layer 700, a second isolation layer 720 positioned on the first isolation layer 710, a first electrode 810 positioned on the second isolation layer 720, a pixel definition layer 830 positioned on the first electrode 810 and the second isolation layer 720, a light emitting layer 900 positioned on the pixel definition layer 830 and the first electrode 810, a photospacer 840 positioned on the pixel definition layer 830, a second electrode 820 positioned on the pixel definition layer 830, the photospacer 840 and the light emitting layer 900.
The pixel definition layer 830 is provided with a first via 3110 correspondingly above the first electrode 810, and the first isolation layer 710 and the second isolation layer 720 are provided with a second via 3150 correspondingly above the TFT layer 700. The light emitting layer 900 contacts the first electrode 810 through the first via 3110, and the first electrode 810 contacts the TFT layer 700 through the second via 3150.
In the aforesaid OLED backplate structure, the first electrode 810 is employed as being a pixel electrode, which is an anode of the OLED, and the second electrode 820 is employed as being a cathode of the OLED, and the thickness of the second electrode 820 is thinner; particularly, in the top light emitting type OLED backplate structure, the transparent electrode has to be manufactured. Thus, a thinner second electrode 820 is required. However, under the circumstance that the second electrode 820 is thinner, the electrical resistance is larger, and particularly in the large scale display, the in plane voltages which is uneven can happen to influence the uniformity of the OLED display and cause issues of uneven brightness (mura).